ISIS fighters and their families as they depart the Lebanon–Syria border zone, Aug. 28, 2017.

WASHINGTON — A bizarre twist to the fight against ISIS is playing out in the Syrian desert, where a convoy of buses filled with hundreds of ISIS fighters and their families has been stranded for more than 10 days.

The US-led coalition has bombed their route, cratering the roads to prevent them from reaching an ISIS stronghold and leaving them stuck in no man’s land. But the US has avoided bombing the buses themselves because of the presence of civilians. Instead, US firepower has been turned on any ISIS fighters who venture from the protection of the buses — to stretch their legs, try to escape, or attend to nature's call.

About 85 fighters have been picked off so far, US Army Col. Ryan Dillon, a spokesman for the US-led coalition, told reporters at the Pentagon on Thursday, speaking from Baghdad.

“We have and will continue to strike ISIS fighters that venture far enough away so we can hit them without causing harm to the civilians that are part of that convoy,” he said.

As the stalemate nears the end of its second week, no one seems to know what comes next.

“We don’t see it as our issue, if you will,” Dillon said. “We’re standing firm [to] do what we can to disrupt ISIS fighters from linking up with their fellow fighters.”

The strange saga began on Aug. 28, when Lebanon's Hezbollah militants and the Syrian government struck a deal with ISIS to remove fighters and their families from their shared border. Syria agreed to give the fighters and their families safe passage to an ISIS-controlled area near Iraq.

But the US objected, and as 17 buses loaded with roughly 300 ISIS fighters and a like number of family members, including women and children, headed toward ISIS-held Deir el-Zour, US forces bombed the roads and a bridge.

With their route made impassable, six buses broke off and headed to territory held by the Syrian government. The remaining 11 have been stuck in the desert for 10 days.

US officials say they've been allowing pickup trucks coming from Syrian-controlled territory to resupply the group with food and water. But the tension is beginning to show among the stranded group.

A few days ago, US officials could see ISIS militants “fighting amongst themselves, brawling in the dirt if you will, after the offload of supplies,” Dillon said. “We chalk that up to frustration among fighters being stuck in the middle of nowhere.”

The ISIS fighters are armed — they'd been allowed to keep small weapons as part of the deal — and a US effort to get Russia to intervene to separate the civilians from the rest of the convoy “has not gained any traction,” Dillon said.

Meanwhile, with no end in sight, all sides have continued to blame each other for the situation of the stranded women and children.

"The Syrian regime is letting women and children suffer in the desert,” the outgoing commander of U.S.-led coalition forces in Iraq and Syria, Lt. Gen. Stephen Townsend, said in a statement. “This situation is completely on them."

The US has denounced the deal to transfer the fighters, arguing in a coalition statement that “relocating terrorists from one place to another for someone else to deal with is not a lasting solution.”

“Irreconcilable ISIS terrorists should be killed on the battlefield, not bused across Syria to the Iraqi border without Iraq’s consent,” the US envoy to the coalition, Brett McGurk, tweeted on Aug. 30.

Evacuating ISIS militants from the border “in air-conditioned cars to their countries is permissible because Lebanon adheres to the philosophy of a state that does not exact revenge,” he told a local radio station, according to the Daily Star, a Lebanese newspaper.

As part of the deal, ISIS militants revealed where they'd buried the bodies of Lebanese soldiers who were kidnapped by the group three years ago.

For its part, Hezbollah claimed the US was “preventing any aid to the convoy which includes sick and wounded people as well as elders,” according to a statement on Sept. 2. “If this situation continues, the imminent death will be the fate of these families, including pregnant women.”

Vera Bergengruen is a Pentagon reporter for BuzzFeed News and is based in Washington, DC.